Heretofore, various forms of venting have been used in molding processes. For example, Dotson U.S. Pat. No. 2,550,140 discloses an air escape vent between the periphery of a rod and the surrounding opening formed in the neck mold of a press or blow mold. The vent is large enough to let air pass therethrough and, yet, small enough to prevent liquid from passing therethrough.
Moslo U.S. Pat. No. 2,976,571 discloses a mold vent which allowed gas to pass therethrough while restricting liquid from passing therethrough. This is done by restricting the opening at the cavity end of the exhaust path of the vent.
Foti U.S. Pat. No. 2,976,568 discloses an injection mold apparatus with a vent and a plunger. The vent serves to allow air to pass therethrough and the plunger is used to clean the vent once the vent becomes clogged with mold material.
Kamiyama et al U.S. Pat. No. 4,822,269 discloses a vent port communicating between first and second nozzles of an injection mold which opens after the mold material has been injected and a reciprocatable screw has been retracted therepast.
Gayso U.S. Pat. No. 4,796,686 discloses a Centrifugal casting machine. The rotation creates a centrifugal force which forces the mold material to the outer edges of the mold. Air and other gases escape through a venturi tube arrangement which is attached to the casting arm and serves to create a vacuum outside the mold cavity which aids in the removal of unwanted gases.